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NASA Contractor Report 189073
Analysis of Lunar Regolith
Thermal Energy Storage
Anthony J. Colozza
Sverdrup Technology, Inc.
Lewis Research Center Group
Brook Park, Ohio
November 1991
Prepared for
Lewis Research Center
Under Contract NAS3-25266
NationalAeronautics and
Space Administration
..
ANALYSIS OF LUNAR REGOLITH THERMAL ENERGY STORAGE
Anthony J. Colozza
Sverdrup Technology Inc.
Lewis Research Center Group
Brook Park, Ohio 44142
ABSTRACT
effective specific
This study w a s performed to evaluate the concept of using
lunar regolith as a thermal energy storage medium. The concept
was examined by mathematically modeling the absorption and
transfer of heat by the lunar regolith. Regolith thermal and
physical properties were established through various sources as
functions of temperature. Two cases were considered: a semiinfinite, constant temperature, cylindrical heat source embedded in a
continuum of lunar regolith and a spherically shaped molten zone of
lunar regolith set with an initial temperature profile. The cylindrical
analysis was performed in order to examine the amount of energy
which can be stored in the regolith throughout a number of lunar
day/night cycles. A constant temperature cylinder was used to heat
the regolith during the day. At night the cylinder acted as a perfect
insulator. This cycling was performed until a "steady state" situation was reached in the surrounding regolith. It was determined
that a cycling "steady staten occurs after approximately 15 day/
night cycles. Results were obtained for cylinders of various diameters. The spherical molten zone analysis was performed to establish the amount of thermal energy, within the regolith, necessary to
maintain some molten material throughout a nighttime period. This
was done by setting the initial conditions within the regolith to
model a molten zone with a surrounding temperature profile and
allowing this to cool for one nighttime period. The surrounding
temperature profile was modeled after the cycling "steady staten
temperature profile established by the cylindrical analysis. It was
determined that a molten sphere diameter of 4.76 m is needed to
maintain a core temperature near the low end of the melting temperature range throughout one nighttime period.
thermal conductivity
SYMBOLS
A
area, m2
C,
constant
C,
constant
c
specific heat, J/kg K
latent heat, J/kg K
heat flux, W/m2
radial distance, m
heat transfer cylinder radius, m
sphere radius, m
temperature, K
time, sec
density, kg/m3
INTRODUCTION
This study was performed to evaluate the concept of using
lunar regolith as a thermal storage medium for a solar dynamic
power system (Crane and Dustin 1991; Barna and Johnson 1968;
Tillotson, 1991). The concept is based on the ability to store
enough high temperature thermal energy within the lunar regolith
during the daytime to allow for continuous power production
throughout the night. Energy would be stored and recovered by
circulating a fluid through a heat transfer device in contact with the
regolith. During the night the heated fluid would then be used to
power a heat engine in order to produce electricity. The thermal
energy could also be extracted for other uses such as materials
processing and space heating.
Thermal energy can be stored within the regolith either
through phase change of the regolith from solid to liquid or as
sensible heat. In order for the concept t o be feasible, the energy
stored during the day must be greater than the thermal losses to the
surroundings throughout the complete day/night cycle.
The ability to use latent heat as the energy storage mechanism
has advantages over sensible heat storage. With latent heat energy
..
perature range of 253 to 1373 K. The conductivity within the regolith melting region, 1373 to 1653 K, was assumed to be a linear
function from the granular value a t 1373 K to the completely
molten rock value at 1653 K. For completely molten or resolidified
regolith, the conductivity was obtained from experimental results on
simulated lunar rock given in Langseth et al., (1973). Resolidified
regolith was considered lunar rock since it is no longer in the
granular form. These conductivity temperature relationships are
shown in Fig. 1.
storage a large amount of energy can be stored without a substantial temperature rise in the regolith. The extraction of this heat
would take place within the melting temperature range of the regolith (1373 to 1653 K), thereby minimizing the variation in the
working fluid temperature of the heat engine. This enables the heat
engine to operate more efficiently.
The concept of storing thermal energy within the regolith was
examined by mathematically modeling the absorption and transfer
of heat by the lunar regolith. Two cases were considered: first, a
semi-infinite, constant temperature, cylindrical heat source embedded in a continuum of lunar regolith. The cylinder dissipates heat
to the surrounding soil which was initially a t equilibrium. Second, a
spherically shaped molten zone of lunar regolith that has an initial
temperature profile from its center to its surface. This situation
assumes sufficient energy has already been deposited t o create the
molten zone. Heat is dissipated to the surrounding soil, which has a
temperature profile extending away from the molten zone that
approximates a %teady state" situation.
The first case examines the amount of energy which can be
stored in the regolith throughout a number of lunar day/night
cycles using a cylindrical heat source as the soil heating mechanism.
The heat source was assumed to be a pipe through which a working
fluid was passed. This pipe would be used to heat the regolith during the day and extract heat during the night. During the day this
is accomplished by conduction from the working fluid, through the
pipe walls, to the surrounding regolith. At night the process is
reversed. The second case examines the heat loss from a molten
sphere of regolith to the surroundings in one night period. This was
performed t o determine the minimum amount of energy necessary in
order to use latent heat as the energy storage mechanism. This part
of the analysis was performed in this manner so it would remove
any dependence on a particular type of heat transfer device. Both
cases approach the problem of heat transfer to and within the regolith in a simplistic manner. In a real life system many additional
factors would need t o be considered. These cases do however establish bounds and on a preliminary basis asses the feasibility of using
lunar regolith for thermal energy storage.
'
1
C, + C2T3
--
(Theorebcal)
%b%
05--
L P C
&YE
$r=a-.,-u,Q ,
-
Figure 1. Conductivity of Granular Lunar Regolith and Lunar
Rock.
The temperature dependence of the regolith thermal conductivity was established as follows: as the temperature of the regolith
increases, its conductivity increases along the granular regolith
curve. Once the initial melting temperature is reached, the conductivity begins to decrease linearly with temperature until the completely molten temperature is reached. This decrease is presumed
due t o the loss in the effective radiation component of the thermal
conductivity as the regolith melts. Conductivity then increases with
temperature along the lunar rock conductivity curve. This conductivity temperature curve is shown in Fig. 2. If the regolith had
obtained a temperature of 1513 K or higher during the heating process it was considered as lunar rock once it began to solidify. Lunar
rock in this context is regarded as fused or molten granular regolith.
In order t o model the heat transfer through the regolith, the
physical properties and characteristics of the soil must be known.
These properties include thermal conductivity, specific heat, latent
heat, density and melting temperature range. The accurate modeling of each property is very important since it's these physical
properties that dictate how the regolith will behave when heated.
The regolith is in granular form up t o a temperature of 1373 I<,
where it will begin to melt. Since the regolith is a mixture of
compounds it melts over a range of temperatures. This melting
temperature range is 1373 t o 1653 K (Langseth e t al., 1973).
Above 1653 K the regolith is completely molten.
The thermal conductivity is dependent on the temperature of
the regolith as well as its physical state (either granular or
solid/liquid). For granular regolith the conductivity was approximated by the following expression (Murase and McBirney, 1970):
-
Lunu Rock (hperimenial)
E
REGOLITH PROPERTIES
k
0
0 Cunu Regohah
(1)
where
C, = 1.281x102,W/m
K
C, = 4.431~10-'~,
W/m
K'
FlqolithTern--
K
Figure 2. - Conductivity Curve of Initial Heating of Granular Lunar
Regolith.
An expression for specific heat was obtained from a curve fit
and interpolation of experimental data given in Robie et al., (1970).
The expression used was:
A plot of this equation is shown in Fig. 1. The values of the
constants, C, and C,, were interpolated from the d a t a given in
Murase and McBirney (1970). For this interpolation, it was
assumed that the ratio between the surface conductivity and the
conductivity a t a depth of 3 m w a s constant throughout the tem-
c = -1848.5 + 1047.41 log(T) J/kg K
2
(2)
<
*
I
Heat In
A plot of this relationship is shown in Fig. 3.
The latent heat of fusion value used was (Crane and Dustin,
1991):
Heptout
Ql = 1429 J/kg K
3000
2500
L
2000
1500
-
1000
Nigh
Thermal
Enercy Edraction
DaytimeThed
500
I
I
0
500
I
I
I
I
1000
l500
Energy storage
-
2000
Figure 4. Daytime and Nighttime Thermal Energy Transfer from
Cylindrical Heat Source.
RegdilhTempernlure%
Figure 3. - Specific Heat Curve for Lunar Regolith.
To solve the equation numerically an explicit finite difference
method was used. The approximations which were selected for the
first and second order derivative terms enabled the equation to be
unconditionally stable (Anderson et al., 1984). The derivative term
approximations are as follows:
This value was added to the specific heat when the temperature
of the regolith reached the initial melting point. The effect of this
can be seen in Fig. 3 where the step increase in the specific heat
throughout the melting region is due to the addition of this latent
heat term. This step increase represents the added ability of the
regolith to absorb energy due to its phase change from solid to
liquid throughout the melting range. This curve can be considered
representative of an effective specific heat given by the following
expression:
T < 1373 K, T > 1653 K
‘eff =
+ Q,
teff = c
1373 K 5 T 2 1653 K
a
(3)
231
ArZ
ar2
(4)
Regolith density was assumed to be constant with a value of
(Lockheed, 1990):
p
To numerically solve this model, the continuum was divided
into concentric cylindrical shells, or nodes, surrounding the heat
source. Boundary conditions were set a t the cylinder radius and at
50 cylinder radii. The value of 50 radii was chosen as the infinity
boundary condition since a t this distance the temperature gradient
within the soil should go to zero (Jenson and Linsley, 1990). The
boundary conditions for daytime heating were:
= li00 kg/m3
CYLINDRICAL HEAT SOURCE ANALYSIS
The cylindrical heat source analysis was performed in order to
model a heated cylinder surrounded by regolith by using the onedimensional, unsteady heat diffusion equation in cylindrical coordinates. A diagram of the cylinder is shown in Fig. 4. For simplicity
it is assumed the axial variation in temperature is negligible. This
equation is given by:
T(rc,t) = 1800 K
(10)
T(50rc,t) = 253 K
(11)
and for nighttime cooling:
(5)
I
Siniplifying yields:
[E 51
+
+
-
k aZT = pceff aT
h2
T(50rc,t) = 253 K
at
These initial conditions are shown in Fig. 5.
As shown previously, thermal conductivity and effective specific
heat are functions of temperature. These functions were substituted
into the above differential equation thereby incorporating the variation of these quantities with temperature into the analysis.
3
(13)
CylindricalHeal Source
1800°K
'i
i
Initial Soil Temperature
5
Figure 5.
- Initial
I
1
!-
I
I
-End
01 1st Day Permd
-n -End 01 41h Day Pwmd
t -End 01 em Day P e r m
Mekinghga
-
1500
i
50 r
I
7
I
253" K
Cylinder Center
Line
A
2000
,
loo0
500
Configuration of Cylindrical Heat Source.
0
2
0
I
I
I
I
4
0
c
10
0
RadidDi&unwfrom PipeCenta(m)
In setting up the analysis, a number of assumptions concerning the heat source had to be made. The cylinder surface was
treated as a constant temperature boundary as opposed to a constant heat flux. Primarily because the buried heat source will be
limited by material constraints as well as solar dynamic concentrator temperature limitations and re-radiation effects. The daytime
cylinder temperature was assumed to be 1800 K. This temperature
is at the upper limit of what the system can be expected to sustain
in continuous use. At night the pipe was assumed to be a perfect
insulator (q = 0). Therefore all heat lost from the system was to
the surroundings. It was further assumed that no other heat loss
mechanisms were present. The analysis was set up to keep track of
the melting history of each node and to use the proper conductivity
relationship for that node depending on that history.
The analysis produced time-dependent radial temperature profiles (node temperature versus position of each node away from
center) of the nodes. For each given cylindrical heat source
diameter, the simulation was run over an increasing number of
day/night heating and cooling cycles until a cycling "steady state"
temperature profile was reached within the regolith surrounding the
cylinder. That is, the cylinder was used to heat the soil through a
number of cycles until the beginning of night (BoN) and beginning
of day (BOD) temperature profiles were the same as the ones from
the previous cycle. This "steady state" situation represents the
maximum amount of energy which can be placed in the soil given
the constraints of the assumed heat pipe temperature, cylinder
diameter and the length of the heating and cooling periods.
-
Figure 6. Temperature Profiles at the End of Each Day Period for
Various Numbers of Cycles.
I
I
2000
I
-End
01 1sI Nqhl Period
-3 -End 01 A T Nmhl Per00
- -End of 8th Nigh1 PDriOa
Mdhng Range
0
2
4
6
0
10
Radial D i h a &om Pipe Center (m)
-
Figure 7. Temperature Profiles a t the End of Each Night Period
for Various Numbers of Cycles.
CYLINDRICAL HEAT SOURCE RESULTS
Temperature profiles were obtained for regolith heating from
cylinder diameters of 1, 1.5 and 2 m, simulating time intervals of up
to 15 lunar day/night cycles. Beyond 15 cycles, the BoN and BOD
temperature profiles no longer changed from cycle to cycle; indicating a "steady state" condition had been reached. The results, shown
in Figs. 6 and 7, were obtained with a 1-m diameter cylindrical heat
source. These figures depict temperature profiles within the surrounding regolith a t various cycles throughout the heating and cooling process. The 1-m diameter cylinder surface temperature for the
15th cycle nighttime period is given in Fig. 8. This figure is an
example of the nighttime output temperature profile which can be
obtained once the cycling "steady state" situation is reached. The
step decrease in the temperature profile slope within the melting
region is due to the release of latent heat energy M the regolith
solidifies. Since the regolith melts over a range of temperatures, as
discussed previously, the ability to extract energy at constant temperature by using the energy released from latent heat is limited. In
this situation latent heat only serves to decrease the rate a t which
the temperature drops as energy is extracted instead of maintaining
a constant temperature.
-
1600
P
$
i8
1500
1400
1300
t.
1200
1100
1000
I
0
5
10
T h e ( Eorlh days)
F
15
Figure 8. - Temperature of 1 m Diameter Cylinder During 15th
Cycle Nighttime Cooling.
4
For various cylinder diameters the cycling “steady state” end of
night (EON) temperature profiles are shown in Fig. 9. The maximum EON temperalure for a 1-m diameter cylinder is below the low
end melting point of the regolith. Consequently, the heat stored
within the regolith is in the form of sensible heat since all the latent
heat energy has dissipated. A cylinder diameter greater then 1.5 m
is required for energy storage in the form of latent heat. For a 2 m
diameter cylinder a small molten zone remains a t the EON. However, the majority of the energy resides as sensible heat in the
surrounding regolith. Due to the temperature limitations on the
cylinder, the regolith temperature profiles do not increase proportionally to cylinder size. As the cylinder size increases, the
corresponding temperature rise in the surrounding regolith dirninislres. This trend can be seen in Fig. 9.
1500
’
I
L
t
1800”K
-1 m Radius Cyhnder
/Temperaturehole
cyclingsteadystate
I
253°K
Line
*
50’s
-
Figure 10. Spherical Molten Zone Initial Conditions.
The spherical analysis was very similar to that for the cylinder.
The governing heat transfer equation was changed to spherical
coordinates given by;
m Radius Cylinder ‘
-a -0 75 m Radius Cylinder
-
I
spherecenter
I
-05
1
2’
Liiear Temperature
DeQvase
.
:-
-simplifying yields;
-_
0
10
20
30
40
The numerical approximations for the derivative terms as well
the as expressions for conductivity, effective specific heat and
density were the same as those used in the cylindrical heat source
analysis. Due t o symmetry, the heat flux at the sphere center is
zero. The boundary conditions used were:
50
Radfd Distance (m)
Figure 9. - EON Cycling Steady State Temperature Profile for
Various Cylinder Sizes.
SPHERICAL MOLTEN
*
ZONE ANALYSIS
A spherical molten zone analysis was also performed in order to
specifically evaluate the concept of using latent heat as the thermal
energy storage mechanism. The analysis was designed to be independent of a particular type of heat transfer device. Therefore the
results can be regarded as a general estimate of the amount of
energy necessary within the regolith to take advantage of latent
heat energy storage. The geometry consisted of a spherical molten
zone surrounded by heated soil. A spherical shape was chosen for
the molten zone since it has the smallest surface area to volume
ratio and is therefore the optimum shape for resisting heat loss.
The analysis was conducted by selecting an initial temperature
profile within the regolith and allowing the regolith to cool for one
night period. The temperature profile within the molten sphere was
assumed t o be linear with a core temperature of 1800 K decreasing
t o the low end melting point temperature of 1373 K. The initial
temperature profile, established in the surrounding soil, began at the
low end melting temperature and decreased according to the BoN
temperature profile which was obtained from the “steady state” cylindrical analysis results. This profile was used since it approximated a cycling “steady state” temperature distribution within the
surrounding soil. With these initial conditions the regolith was
allowed to cool for one night period. A diagram of these initial
conditions are shown in Fig. 10.
The size of the molten sphere was adjusted until a small
portion of regolith at the core remained a t or above 1373 K
throughout the night period. The analysis was structured in this
manner in order t o determine the feasibility of using latent heat as
the energy storage mechanism and to estimate both heat loss and
required thermal energy within the regolith.
q(0,t) = 0.0
(16)
T(50r,,t) = 253 K
(17)
Once the required sphere size was determined, the corresponding temperature profile within the sphere and surrounding soil was
used to calculate the amount of thermal energy remaining within
the soil. By comparing this with the energy initially in the soil,
obtained from the initial temperature profile, an estimate can be
obtained of the losses t o the surroundings. In addition the total
thermal energy initially stored within the regolith, in order to
maintain a molten region throughout the night period, can be
determined.
SPHERICAL MOLTEN ZONE RESULTS
diameter molten sphere is
It was determined that a 4.76-111
necessary in order to maintain a core temperature near the lower
limit of the melting range after one night period. This result is
shown in Fig. 11. From the initial and final temperature profiles for
this size sphere, heat losses and required energy were calculated.
These are listed in Table I.
5
One point that should be made is that both the cylinder and
molten sphere analysis were for minimally sized systems, that is no
energy was extracted to do work. So for a system, operating under
the same conditions and assumptions, in which thermal energy is
extracted throughout the night the resulting EON temperature profiles would be lower and more energy would need to be supplied
during the day period then what was shown in this analysis.
Since this was a numerical analysis, various assumptions had to
be made which, if changed, could alter the results and conclusions.
Also, for simplicity reasons, various factors were not considered in
the analysis; these factors could also have an effect on the results.
A summary of some issues which should be considered if a more
detailed analysis is to be performed are as follows:
(1) Examination of convection heat transfer within the molten
regolith to determine if this will allow larger amounts of heat to be
transferred to the regolith.
(2) Two-dimensional analysis which would take into account
radiative heat losses from the surface of the heated region to the
sky.
(3) Consideration of the effect the formation of voids would
have if they formed during the regolith melting and resolidification
process.
(4) Issue of replenishing regolith material due t o the increase in
density when it transitions from the granular to molten and or solid
state.
(5) Re-examination of regolith properties to asses their validity.
Possibly conduct an experiment to directly determine these properties for circumstances similar to those under the proposed system.
(6) Examination of the effects of out-gassing and chemical reactions which may occur when the regolith is heated, this may
increase conductivity.
2000
Temperalure
+Final
-
9
1500
I!
E
1000
F
B
j
500
0
0
5
10
20
15
25
35
30
40
RndialDistnrrs branSphueCenter(m)
Figure 11.- Initial and Final Temperature Profiles for a 4.76 m
Diameter Spherical Molten Zone.
TABLE 1. - THERMAL ENERGY STORED IN
REGOLITH BEFORE AND AFTER NIGHTTIME
COOLING
I
I
f
I
I
BoN energy
in regolith,
Mol ten region
Surrounding soil
Total svstem
1.95~10”
1.83~10’~
1.85~10’~
EON energy
in regolith,
1.09x 10“
1.71~10’~
1.72~10’~
Percent of latent energy lost from the molten zone,
percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Percent of total energy lost from the molten zone,
percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Percent of energy lost from the total system,
percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
By examining the results it is evident that the ability to store a
sufficient amount of energy in the form of latent heat is questionable. However, a substantial amount of energy is stored as sensible
heat.
There is a substantial advantage in being able to store energy
in a substance which is already present on the lunar surface. Even
if the use of sensible heat to operate a heat engine proves to be undesirable this method of storing energy may still be applicable for
other uses such as space heating or material processing. Regardless
of the application, any use of this type of storage can substantially
increase our ability to explore and inhabit our closest neighbor, the
moon.
100
44
CONCLUDING REMARKS
The results have shown that a cycling ‘steady state” exists for
a cylindrical heat transfer device within the regolith. By examining
the temperature profiles for the cylinder once this steady state situation is reached, it can be seen that a cylinder size greater then
1.5 m in diameter is necessary to maintain some molten material
throughout the night period. Below this size, no matter how many
day/night cycles the system experiences, no molten material will
remain after the night period. By using a more efficient heat
transfer device, that is one which can transfer a larger quantity of
energy into the regolith, the necessary size may be reduced. However, it can also be concluded that the heat transfer device will need
to be distributed throughout the desired molten region. This can
lead to a complicated deployment scheme as well as the need for
substantial infrastructure. Regardless of the heat transfer device
configuration, it cannot be readily assumed that the desired regolith
temperatures can be achieved by running the system for a number of
daylnight cycles. Each device after a given number of cycles will
reach a cycling “steady state” which may or may not produce the
desired regolith temperature.
The spherical molten zone results show that a minimum size
(surface area to volume ratio) is necessary to maintain any latent
heat through the lunar night. To build up a molten zone of this size
a substantial amount of energy, in the form of low grade heat, must
be deposited first. But the high grade heat within this molten zone,
like the peak of a pyramid, is most rapidly dissipated by the natural
losses.
REFERENCES
Anderson, D.A., Tannehill, J.C., and Pletcher, R.H., 1984, Computational Fluid Mechanics and Heat Transfer, Hemisphere Publishing Corp., New York.
Barna, G.J. and Johnson, R.L., 1968 ‘Investigation of the use of
the Lunar Surface Layer to Store Energy for Generating Power
During the Lunar Night,” NASA T M X-1560.
Crane, R.A. and Dustin, M.O., 1991, “Solar Dynamic Power/
Process Heat Generation for the Proposed Lunar Oxygen Production Plant,” NASA Lewis Internal Report.
Horai, K. and Fujii, N., 1972, “Thermophysical Properties of
Lunar Material Returned by Apollo Missions,” The Moon, Vol. 4,
pp, 447-475.
Jenson, E.B. and Linsley, J.N., 1990, “Waste Heat Rejection
System for a Lunar Oxygen Production Plant,” Engineering, Construction and Operations in Space 11, S.W. Johnson and
J.P. Wetzel, eds., ASCE, New York, Vol. 1, pp. 378-388.
Langseth, M.G., Jr., Keihm, S.J., and Chute, J.L., Jr., 1973,
‘Heat Flow Experiment,” Apollo 17 Preliminary Science Report
NASA SP-330, Chapt. 9.
6
I
\.
-
Tillotson, B., 1991, 'Regolith Thermal Energy Storage for Lunar
Nighttime Power," AIAA Paper 91-3420.
West, G.S., Jr., Wright, J.J., and Euler, M.C., eds., 1977, 'Space
and Planetary Environment Criteria Guidelines for Use in Space
Vehicle Development," NASA TM-78119.
Lockheed Engineering and Sciences Company, Inc., Preliminary
Report, Lunar Data Base, Apr. 20, 1990.
Murase, T. and McBirney, A.R., 1970, "Thermal Conductivity of
Lunar and Terrestrial Igneous Rocks in Their Melting Range,"
Science, Vol. 170, pp. 165-167.
Robie, R.A., Hemingway, B.S., and Wilson, W.H., 1970, 'Specific
Heats of Lunar Surface Materials from 90 to 350 K," Apollo 11
Lunar Science Conference, Pergamon Press, Vol. 3, pp. 2361-2367.
Rowley, J.C. and Neudecker, J.W., 1985, 'In-Situ Rock Melting
Applied to Lunar Base Construction and for Exploration Drilling
and Coring on the Moon," Lunar Bases and Space Activities for the
21st Century, W.W. Mendell, ed., Lunar and Planetary Institute,
Houston, TX, pp. 165-477.
,
7
Form Approved
REPORT DOCUMENTATION PAGE
. AGENCY USE ONLY (Leaveblank)
OMB NO.0704-0188
3. REPORT TYPE AND DATES COVERED
2. REPORT DATE
November 1991
Final Contractor Report
I
I
5. FUNDING NUMBERS
1. TITLE AND SUBTITLE
Analysis of Lunar Regolith Thermal Energy Storage
WU-591-14-11
1. AUTHOR(S)
Anthony J. Colozza
r.
8. PERFORMING ORGANIZATION
REPORT NUMBER
PERFORMING ORQANIZATIONNAME(S) AND ADDRESS(ES)
Sverdrup Technology, Inc.
Lewis Research Center Group
2001 Aerospace Parkway
Brook Park, Ohio 44142
None (E-6680)
IO. SPONSORING/MONITORING
#. SPONSORING/MONITORING AGENCY NAMES(S) AND ADDRESS(ES)
AGENCY REPORT NUMBER
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135-3191
NASA CR-189073
11. SUPPLEMENTARY NOTES
Project Manager, David J. Bents, Power Systems Integration Office, NASA Lewis Research Center, (216)433- 6135.
Prepared for the International Solar Energy Conference sponsored by the American Society of Mechanical Engineers,
Lahaina, Maui, Hawaii, April 4-8, 1992.
I
12b. DISTRIBUTION CODE
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Subject Categories 44 and 34
15. NUMBER OF PAGES
14. SUBJECT TERMS
8
Solar dynamic power system; Regolith; Heat storage;
Thermal energy; Numerical analysis
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